• Authors:
    • Mehuys, G. R.
    • Madramootoo, C. A.
    • Burgess, M. S. E.
    • Mehdi, B. B.
    • Dam, R. F.
    • Callum, I. R.
  • Source: Soil & Tillage Research
  • Volume: 84
  • Issue: 1
  • Year: 2005
  • Summary: Different tillage and residue practices could potentially lead to significant differences in both crop production and soil properties, especially if both practices are implemented over a long time period and on continuous monoculture corn (Zea mays L.). The objective of this research was to determine how differing tillage practices and corn residues affected soil bulk density, corn emergence rates and crop yields over an 11-year period. The experimental site consisted of three tillage practices (no-till, NT; reduced tillage, RT; and conventional tillage, CT) and two residue practices (with grain corn residue, R; without residue (corn crop harvested for silage), NR). Bulk density was 10% higher in NT (1.37 Mg m(-3)) than in CT (1.23 Mg m(-3)), particularly at the 0-0.10 m depth. Spring corn emergence in NTR was slower by 14-63% than all other treatments in 1992-1994. In 1996, corn emergence in the NTR treatment was 18-30% slower, and NTNR was 5-30% faster than all other treatments. No-till with residue (NTR) possibly had the slowest overall emergence due to the higher surface residue cover (8.5 Mg ha(-1) in 1996) and higher bulk density (1.37 Mg m(-3) over the 11 years). Long-term mean dry matter corn yields were not affected by tillage and residue practices during the course of this study; rather climatic-related differences seemed to have a greater influence on the variation in dry matter yields. The long-term cropping of corn under different tillage and residue practices can change bulk density in the surface soil layer, vary the corn emergence without affecting yields, and produce comparable yields between all the tillage and residue practices. (C) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Shea, K. L.
    • Gregory, M. M.
    • Bakko, E. B.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 20
  • Issue: 2
  • Year: 2005
  • Summary: We compared soil characteristics, runoff water quantity and nutrient fluxes, energy use and productivity of three farm types in an unusually dry farming season: conventional (continuous corn and deep tillage), rotation (5-year corn-soybean-oats/ alfalfa-alfalfa-alfalfa rotation with tillage 2/5 years) and no-till (corn-soybean with no cultivation). Soil organic matter content was highest on the rotation farm, followed by the no-till farm, and lowest on the conventional farm. Nitrate content of the soil did not differ significantly among the three farms, although the conventional farm had a much higher input of fertilizer nitrogen. Soil penetrometer resistance was lower and percent soil moisture was higher in the no-till and rotation systems compared to the conventional farm. Soil macroinvertebrate abundance and diversity were highest on the no-till farm, followed by the rotation farm. No invertebrates were found in the soil of the conventional farm. The conventional farm had the highest runoff volume per cm rain and higher nitrogen (N) loss in runoff when compared to the rotation and no-till farms, as well as a higher phosphorus (P) flux in comparison to the no-till farm. These results indicate that perennial close-seeded crops (such as alfalfa) used in crop rotations, as well as plant residue left on the surface of no-till fields, can enhance soil organic content and decrease runoff. The lower soil penetrometer resistance and higher soil moisture on the rotation and no-till farms show that conservation tillage can increase soil aggregation and water infiltration, both of which prevent erosion. Furthermore, crop rotation, and particularly no-till, promote diverse invertebrate populations, which play an important role in maintaining nutrient cycling and soil structure. Crop rotation and no-till agriculture are less fossil-fuel intensive than conventional agriculture, due to decreased use of fertilizers, pesticides and fuel. In this unusually dry year they provided superior corn and soybean yields, most likely due to higher soil moisture as a result of greater water infiltration and retention associated with cover crops (rotation farm) and crop residue (no-till farm).
  • Authors:
    • Wolt, J. D.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 69
  • Issue: 1
  • Year: 2004
  • Summary: The effectiveness of nitrification inhibitors for abatement of N loss from the agroecosystem is difficult to measure at typical agronomic scales, since performance varies at the research field scale due to complex interactions among crop management, soil properties, length of the trial, and environmental factors. The environmental impact of the nitrification inhibitor nitrapyrin on N losses from agronomic ecosystems was considered with emphasis on the Midwestern USA. A meta-evaluation approach considered the integrated responses to nitrification inhibition found across research trials conducted in diverse environments over many years as measured in side- by-side comparisons of fertilizer N or manure applied with and without nitrapyrin. The resulting distributions of response indices were evaluated with respect to the magnitude and variance of the agronomic and environmental effects that may be achieved when nitrification inhibitors are used regionally over time. The indices considered (1) crop yield, (2) annual or season-long maintenance of inorganic N within the crop root zone, (3) NO3-N leached past the crop root zone, and (4) greenhouse gas emission from soil. Results showed that on average, the crop yield increased (relative to N fertilization without nitrapyrin) 7% and soil N retention increased by 28%, while N leaching decreased by 16% and greenhouse gas emissions decreased by 51%. In more than 75% of individual comparisons, use of a nitrification inhibitor increased soil N retention and crop yield, and decreased N leaching and volatilization. The potential of nitrification inhibitors for reducing N loss needs to be considered at the scale of a sensitive region, such as a watershed, over a prolonged period of use as well as within the context of overall goals for abatement of N losses from the agroecosystem to the environment.
  • Authors:
    • Halvorson, A. D.
    • DeVuyst, E. A.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 1
  • Year: 2004
  • Summary: Annualized yields with more intensive cropping (IQ systems tend to be greater than those of spring wheat-fallow (SW-F); however, little economic comparison information is available. The long-term (12 yr) effects of tillage system and N fertilization on the economic returns from two dryland cropping systems in North Dakota were evaluated. An IC rotation [spring wheat (Triticum aestivum L.)winter wheat (T. aestivum L.)-sunflower (Helianthus annuus L.)] and a SW-F rotation were studied. Tillage systems included conventional till (CT), minimum till (MT), and no-till (NT). Nitrogen rates were 34, 67, and 101 kg N ha(-1) for the IC system and 0, 22, and 45 kg N ha(-1) for the SW-F system. Annual precipitation ranged from 206 to 655 mm, averaging 422 mm over 12 yr. The IC system generated higher profits than the SW-F system, but the IC profits were more variable. Within the IC system, MT generated higher profits than corresponding N treatments under CT and NT, but MT profits were more variable. Of the N rates evaluated, the largest N rates generated the largest profits. The dryland IC system with MT and NT was more profitable than the best SW-F system using CT for this location. Stochastic dominance analyses revealed that the SW-F system and IC system CT treatments were economically inefficient when compared with the IC system with MT and NT.
  • Authors:
    • Levesque, G.
    • Prevost, D.
    • Chantigny, M. H.
    • Belanger, G.
    • Angers, D. A.
    • Rochette, P.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 2
  • Year: 2004
  • Summary: There is considerable uncertainty relative to the emissions of N2O from legume crops. A study was initiated to quantify N2O fluxes from soils cropped to alfalfa (Medicago sativa L.) and soybean (Glycine max L.), and to improve our understanding of soil and climatic factors controlling N2O emissions from these crops. Measurements were made on three soils cropped to alfalfa, soybean, or timothy (Phleum pratense L.), a perennial grass used as a control. In situ soil-surface N2O emissions (FN2O) were measured 47 times during the 2001 and 2002 growing seasons. Soil water, NH4-N, NO3-N, and N2O contents, and soil temperature were also determined to explain the variation in gas fluxes. Emissions of N2O were small under the grass where very low soil mineral N content probably limited denitrification and N2O production. Soil mineral N contents under legumes were up to 10 times greater than under timothy. However, soil mineral N contents and FN2O were not closely related, thus suggesting that the soil mineral N pool alone was a poor indicator of the intensity of N2O production processes. Higher FN2O were measured under legume than under timothy in only 6 out of 10 field comparisons (site-years). Moreover, the emissions associated with alfalfa (0.67-1.45 kg N ha-1) and soybean (0.46-3.08 kg N ha-1) production were smaller than those predicted using the emission coefficient proposed for the national inventory of greenhouse gases (alfalfa = 1.60-5.21 kg N ha-1; soybean = 2.76-4.97 kg N ha-1). We conclude that the use of the current emission coefficient may overestimate the N2O emissions associated with soybean and alfalfa production in eastern Canada.
  • Authors:
    • Paustian, K.
    • Mosier, A. R.
    • Conant, R. T.
    • Breidt, F. J.
    • Ogle, S. M.
    • Six, J.
  • Source: Global Change Biology
  • Volume: 10
  • Issue: 2
  • Year: 2004
  • Summary: No-tillage (NT) management has been promoted as a practice capable of offsetting greenhouse gas (GHG) emissions because of its ability to sequester carbon in soils. However, true mitigation is only possible if the overall impact of NT adoption reduces the net global warming potential (GWP) determined by fluxes of the three major biogenic GHGs (i.e. CO2, N2O, and CH4). We compiled all available data of soil-derived GHG emission comparisons between conventional tilled (CT) and NT systems for humid and dry temperate climates. Newly converted NT systems increase GWP relative to CT practices, in both humid and dry climate regimes, and longer-term adoption (>10 years) only significantly reduces GWP in humid climates. Mean cumulative GWP over a 20-year period is also reduced under continuous NT in dry areas, but with a high degree of uncertainty. Emissions of N2O drive much of the trend in net GWP, suggesting improved nitrogen management is essential to realize the full benefit from carbon storage in the soil for purposes of global warming mitigation. Our results indicate a strong time dependency in the GHG mitigation potential of NT agriculture, demonstrating that GHG mitigation by adoption of NT is much more variable and complex than previously considered, and policy plans to reduce global warming through this land management practice need further scrutiny to ensure success.
  • Authors:
    • Li, C.
    • Lemke, R.
    • Desjardins, R. L.
    • Grant, B.
    • Smith, W. N.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 68
  • Issue: 1
  • Year: 2004
  • Summary: The DNDC model was used to estimate direct N2O emissions from agricultural soils in Canada from 1970 to 1999. Simulations were carried out for three soil textures in seven soil groups, with two to four crop rotations within each soil group. Over the 30-year period, the average annual N2O emission from agricultural soils in Canada was found to be 39.9 Gg N2O-N, with a range from 20.0 to 77.0 Gg N2O-N, and a general trend towards increasing N2O emissions over time. The larger emissions are attributed to an increase in N-fertilizer application and perhaps to a trend in higher daily minimum temperatures. Annual estimates of N2O emissions were variable, depending on timing of rainfall events and timing and duration of spring thaw events. We estimate, using DNDC, that emissions of N2O in eastern Canada (Atlantic Provinces, Quebec, Ontario) were approximately 36% of the total emissions in Canada, though the area cropped represents 19% of the total. Over the 30-year period, the eastern Gleysolic soils had the largest average annual emissions of 2.47 kg N2O-N ha-1 y-1 and soils of the dryer western Brown Chernozem had the smallest average emission of 0.54 kg N2O-N ha-1 y-1. On average, for the seven soil groups, N2O emissions during spring thaw were approximately 30% of total annual emissions. The average N2O emissions estimates from 1990 to 1999 compared well with estimates for 1996 using the IPCC methodology, but unlike the IPCC methodology our modeling approach provides annual variations in N2O emissions based on climatic differences.
  • Authors:
    • McConkey, B.
    • Zhang, Z.
    • Goddard, T. W.
    • Lemke, R. L.
    • Izaurralde, R. C.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 4
  • Year: 2004
  • Summary: Nitrous oxide fluxes from soils are inherently variable in time and space. An improved understanding of this variability is needed to make accurate estimates of N2O fluxes at a regional scale. The objectives of this work were to (i) characterize the influence of soil-landscape combinations and N application rates on N2O emissions and to (ii) determine the contribution of these influences on the estimation of N2Oemissions at the field scale.We used static chambers and gas chromatography methods to measure N2O fluxes and collected ancillary data (mineral N, water soluble C, soil water content, soil temperature) in Canada at Mundare (AB) in the aspen parkland ecoregion and at Swift Current (SK) in the short-grass prairie eco-region. At Mundare, measurements were taken in 1995 and 1996 by landscape position and land use.At Swift Current, data were collected in 1999 and 2000 by landscape position and N rate. At Mundare, landscape position affected N2O emissions but the pattern varied seasonally. During a 46-d period in summer 1995, a flux of 430 g N2O-N ha-1 measured in a backslope was greater than the 60 g N2O-N ha-1 measured on average in shoulder and depressional areas. The flux pattern changed during a 43-d spring thaw of 1996 when fluxes from depressional areas were greatest (1710 g N2O-N ha-1). Nitrous oxide emissions from natural areas were small. The emission pattern during summer 1996 was similar to that of 1995 but the fluxes were an order of magnitude larger. At Swift Current, N2O fluxes in summer 1999 were affected by topography and N rate. Fluxes were greatest in depressional areas receiving N at 110 kg ha-1 (3140 g N2O-N ha-1). Use of the area fraction occupied by each landscape position to calculate N2O flux increased the estimates of N2O fluxes at the field scale in five out of six cases. Further research of N2O fluxes in variable landscapes should help elucidate factors controlling N2O fluxes from pedon to field scale and thus translate into improved flux estimates at regional scales.
  • Authors:
    • Dale, B. E.
    • Kim, S.
  • Source: Biomass and Bioenergy
  • Volume: 26
  • Issue: 4
  • Year: 2004
  • Summary: The global annual potential bioethanol production from the major crops, corn, barley, oat, rice, wheat, sorghum, and sugar cane, is estimated. To avoid conflicts between human food use and industrial use of crops, only the wasted crop, which is defined as crop lost in distribution, is considered as feedstock. Lignocellulosic biomass such as crop residues and sugar cane bagasse are included in feedstock for producing bioethanol as well. There are about 73:9 Tg of dry wasted crops in the world that could potentially produce 49:1 GL year-1 of bioethanol. About 1:5 Pg year-1 of dry lignocellulosic biomass from these seven crops is also available for conversion to bioethanol. Lignocellulosic biomass could produce up to 442 GL year-1 of bioethanol. Thus, the total potential bioethanol production from crop residues and wasted crops is 491 GL year-1, about 16 times higher than the current world ethanol production. The potential bioethanol production could replace 353 GL of gasoline (32% of the global gasoline consumption) when bioethanol is used in E85 fuel for a midsize passenger vehicle. Furthermore, lignin-rich fermentation residue, which is the coproduct of bioethanol made from crop residues and sugar cane bagasse, can potentially generate both 458 TWh of electricity (about 3.6% of world electricity production) and 2:6EJ of steam. Asia is the largest potential producer of bioethanol from crop residues and wasted crops, and could produce up to 291 GL year -1 of bioethanol. Rice straw, wheat straw, and corn stover are the most favorable bioethanol feedstocks in Asia. The next highest potential region is Europe (69:2 GL ofbioethanol), in which most bioethanol comes from wheat straw. Corn stover is the main feedstock in North America, from which about 38:4 GL year -1 of bioethanol can potentially be produced. Globally rice straw can produce 205 GL of bioethanol, which is the largest amount from single biomass feedstock. The next highest potential feedstock is wheat straw, which can produce 104 GL of bioethanol. This paper is intended to give some perspective on the size ofthe bioethanol feedstock resource, globally and by region, and to summarize relevant data that we believe others will 0nd useful, for example, those who are interested in producing biobased products such as lactic acid, rather than ethanol, from crops and wastes. The paper does not attempt to indicate how much, if any, of this waste material could actually be converted to bioethanol.
  • Authors:
    • Wienhold, B. J.
    • Tanaka, D. L.
    • Liebig, M. A.
  • Source: Soil & Tillage Research
  • Volume: 78
  • Issue: 2
  • Year: 2004
  • Summary: The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA1: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0-7.5, 7.5-15, and 15-30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop-fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mgha-1), particulate organic matter C (POM-C) (by 4.98Mgha-1), potentially mineralizable N (PMN) (by 32.4 kg ha-1), and microbial biomass C (by 586 kg ha-1), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h-1) relative to the crop-fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha-1 for PMN; 792 kg ha-1 for microbial biomass C) as compared with sequences with fallow (SW-S-F and SW-F) (Average = 15.9 kg ha-1 for PMN; 577 kg ha-1 for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.